Pulse generator



Match 17, 1959 LLIO T 2,878,438

PULSE GENERATOR Filed March 27. 1956 11c. 24 I POWER SUPPLY W i 35 I l l I FIG. 2 FIG. 3

INVENTOR GEORGE ELLIOTT BY ATTORNEV United States Patent PULSE GENERATOR George Elliott, Rochester, N. Y., assiguor to General Dynamics Corporation, Rochester, N. Y., a corporation of Delaware Application March 27, 1956, Serial No. 574,193

6 Claims. (Cl. 321-49) This invention relates to power supply devices in the field of communication means and particularly to means for supplying a source of pulsating currents for signalling purposes.

The object of the invention is to provide a simple, rugged, reliable and economical source of pulsating current such as that used in the telephone plant for ringing current. Basically, a polarized relay of the type that requires energization in one direction to drive the relay in one direction and a substantially equal energization in the other direction to return the relay to its first position is employed in a self-operating circuit, with means being provided to adjust the speed of operation to thereby control the periodicity of the output and means to control the relative periods of dwell in the two positions thereof.

A feature of the invention is the use of a mercury wetted contact relay, capable of handling comparatively heavy currents over a long life and requiring no contact adjustment usually resulting from contact wear.

Another feature of the invention is the use of a balanced self-operating network terminating in a front and a back contact of the relay with the coil thereof bridged across this network and having a balance rheostat bridged across said winding whereby the relative speed of movement of the armature in opposite directions may be adjusted to produce either equal or unequal periods of dwell of the armature on its opposed contacts, the remainder of the network including resistance and capacity components properly chosen with respect to the impedance of the coil to produce a desired range of speed of operation of the relay. By such means a relay inverter may be provided capable of sustained operation at a distant unattended ofi'ice and which, after adjustment for speed of operation and percentage dwell on its contacts, will function reliably.

Another feature of the invention is the use of a relay having an armature, a pair of front contacts and a pair of back contacts. One front and one back contact are used in the self-operating relay network and the other front and back contacts are used in the load circuit, the armature being connected to one pole of a direct current source used both for driving the relay and for alternately transmitting a square topped pulse to the two terminals of a mid-tapped primary winding of an output transformer.

'Another feature of the invention is the use of the two coils of a transformer, oppositely poled in the leads between the relay contacts and the primary winding of the output transformer for producing a constant voltage output of this derived pulsating current.

Other features will appear hereinafter.

The drawings consist of one sheet having three figures, as follows.

Fig. 1 is a schematic circuit diagram showing the circuit elements and connections used for carrying out the present invention;

Fig. 2 is an applique circuit which may be patched into Fig. 1 to provide one form of the invention; and

Fig. 3 is-an applique circuit which may be similarly patched into Fig. l to provide another form of the invention.

Heretofore devices employed for the purposes of pro viding a supply of pulsating current such as the ringing current for telephone systems have been large, cumbersome, expensive and subject to the ills of contact erosion, so that the cost of maintenance was an important factor.

By the use of a now commercially obtainable mercury wettcd contact relay requiring a substantially insignificant amount of power for its operation, a reliable, long life relay type inverter may be provided for the supply of ringing current in distantly located unattended offices.

The relay employed in a specific embodiment of the present invention is of the general type comprised of a single mercury contact switch enclosed with an operating coil in a steel vacuum tube housing. The switch is used as the core of the coil which provides the operating magneto-motive force. The steel housing provides mechanical protection for the coil and switch, and also reduces the magnetic coupling between adjacently mounted relays and increases the magnetic efiiciency. Terminals for the switch and coil are on a standard medium-sized octal base, and the relay can easily be inserted in a circuit in the same manner as a vacuum tube. A glass envelope hermetically seals the armature and contact assemblies in a high pressure hydrogen atmosphere. The switch has two front contacts, two back contacts and a single swinger. Except for the steel housing of the relay, the magnetic circuit is all contained within the glass envelope and is common to part of the contact structure. The swinger or armature of the switch consists of a cantilever reed structure projecting from the bottom end of the glass envelope and interposing the two sets of fixed contacts supported from the top end. Mercury-wetting on the fixed and moving contacting surfaces is maintained by a capillary feed system, associated with the cantilever reed, and connected to a reservoir at the bottom of the switch. Mercury-wetting and gas under pressure as well as the small size of parts result in a combination of performance capabilities which include high speed, freedom from chatter, high current and voltage handling capacity and constancy of performance. The mercury performs three important functions; (1) it provides continuously replenished contact surfaces and avoids deterioration of the underlying metal, (2) it serves to dampen undesirable modes of vibration of the armature, and (3) it bridges over the mechanical chatter between the underlying metal contact surfaces. The resistance of the contacts including that of the internal wiring between base terminals is extremely low. The switch element is permanently biased by the inclusion of small permanent magnet elements and is so adjusted that the swinger will remain in contact with either the front or the back contacts until driven to the opposite contacts by an energization of the coil in one direction or the other.

Looking at Fig. 1 it will be seen that a button or key 1 is provided to place the device in operation. Closure of the contact by key 1 operates the ST relay 2 in an obvious circuit whereupon the armatures 3 and 4 move to close circuits to their front contacts.

Armature 4 is connected to the grounded plus terminal of a source of direct current 5, so that a circuit is then closed through a rheostat 7 constituting a speed control, thence through a second rheostat 8 constituting a balance control, thence through a resistor 12, the coil of the relay connected to the seventh and eighth pins of the relay mounting, resistors 10 and 11 to the back contact connected to the fourth pin of the relay mountasrfsgrse e in cuit is then closedthrough resistors .9, 13 and 14 and the coil in the reverse direction to return the armature to the position shown.

By means of the capacitor 15, bridged across the coil and the capacitor 16 connected from the junction of resistors 13 and 14 to the junction of resistors and 11, the movement of the armature may be timed. This timing may be varied to a given extent by the rheostat 7 so that the speed of operation may be accurately adjusted. By means of the balance rheostat 8, the current flow through the coil in the two opposite directions may be adjusted so that the dwell of the armature on the front and back contacts may be made equal or different as desired. Thus the relay may be driven constantly at an accurately adjusted rate and since the work performed thereby does not affect its operating circuits, its operation will be independent of the load.

The load circuit controlled by the relay includes the negative terminal of the direct current power supply applied alternately to conductors 17 and 18 by the armature and the two contacts of the relay connected respectively to pins 1 and 5 of the relay mounting. The resistors 19 and 20 and condensers 21 and 22 constitute contact protection networks for these relay contacts.

When the negative battery terminal is connected through a contact of the relay to conductor 17, a circuit is then extended either through the circuit of Fig. 2 or the circuit of Fig. 3 to the upper half of the primary coil of transformer 23, the armature 3 of relay 2, the inductor 24 to the plus or ground terminal of the direct current power supply. When the armature of the relay moves to its opposite position, current is then caused to flow through the lower half of the primary of transformer 23 and the currents alternately applied to the two halves of this primary winding produce an alternating or pulsating current in the secondary thereof so that the terminals 24 and 25 become the terminals of a source of pulsating current which may be used as ringing current.

Fig. 2.or Fig. 3 may be patched into Fig. 1 in the space 26 so as to provide alternative circuit arrangements. By the use of a transformer 27 connected as indicated in Fig. 3, a constant voltage output may be had at the terminals 24 and 25. By the use of the direct connections indicated in Fig. 2 a simpler and less expensive circuit may be provided where it is unnecessary to have a constant voltage output.

What is claimed is:

l. A relay inverter for deriving an alternating pulsating current from a source of direct current consisting of a mercury-Wetted contact polarized relay constructed and arranged to hold its armature on either its front or its back contacts, included in a circuit whereby its coil will always be connected by its armature and the contact to which it has been driven to impel the said armature to the opposed contacts, a means included in said circuit for adjusting the speed of operation of said relay, another means included in said circuit for adjusting the relative periods of dwell on said contacts and a circuit operated by said relay for alternately connecting a direct current source to the opposite wires of an output circuit.

2. A relay inverter for deriving an alternating pulsating current from a source of direct current consisting of a mercuryetted contact polarized relay included in a self-operating circuit network having a speed controlling rheostat in series therewith and a balance rheostat in said network for adjusting the relative rate. of movement of said relay in opposite directions to control the relative periods of dwell on its said back and front contacts, a load circuit for said device including means operated by said relay for alternately applying one pole of a direct current source to each side of said load circuit.

3. A relay inverter for deriving an alternating pulsating current from a source of direct current consisting of a terna t ed n st q ize relay h i an rm- 4 ture, a pair of back contacts and apair of front contacts therefor, said relay being included in a self-operating circuit network connected to one of said pair of back contacts and one of said pair of front contacts, a speed controlling rheostat in series therewith and a balance rheostat in said network for adjusting the relative speed of movement of said armature in opposite directions to control the relative periods of dwell of said armature on its said back and front contacts, a load circuit including said armature, a front and a back contact, a transformer having mid-tap primary and a source of direct current connected to said armature and to said primary mid-tap, the ends of said primary winding being connected to the other of said pair of back contacts and the other of said pair of front contacts, whereby a direct current path from said armature through each half of said primary Winding will be altelnately established.

4. A relay inverter for deriving an alternating pulsating current from a source of direct current consisting of a mercuryetted contact polarized relay having an armature, a pair of back contacts and a pair of front contacts therefor, said relay being included in a self-operating circuit network connected to one of said pair of back contacts and one of said pair of front contacts, a speed controlling rheostat in series therewith and a balance rheostat in said network for adjusting the relative speed of movement of said armature in opposite directions to control the relative periods of dwell of said armature on its said back and front contacts, a load circuit including said armature, the other of said pair of front contacts and the other of said pair of back contacts being connected to the ends of the primary winding of a transformer having a mid-tap primary and a source of direct current connected to said armature and to said primary mid-tap and another transformer having its primary and secondary winding serially included in the two conductors of said load circuit between said armature and said other of said pair of back contacts and said other of said pair of front contacts and said primary winding of said first transformer.

5. A relay inverter for deriving an alternating pulsating curent from a source of direct current consisting of a polarized relay of the type in which its armature will remain in contact with either its front or back contacts to which it was last driven, an armature, a pair of front contacts and a pair of back contacts for said relay, said relay being included in a self-operating network includ' ing a coil for said relay and said armature, one of said front contacts and one of said back contacts, a source of direct current connected to said network, a speed controlling rheostat in series with said network and a balance rheostat in said network for adjusting the relative speed of movement of said armature in opposite directions to control the relative periods of dwell of said armature on its said back and front contacts, a load circuit including said armature, a front and a back contact therefor and a pair of wires connected to said contacts and leading to the primary winding of an output transformer, said primary winding having a mid-tap and connections from said source of direct current made to said armature and said mid-tap.

6. A relay'inverter for deriving an alternating pulsating current from a source of direct current consisting of a polarized relay of the type in which its armature will remain in contact with either its front or back contacts to which it was last driven, a winding, an armature, a pair of front contacts and a pair of back contacts for said relay, said winding, a said front contact and a said back contact being included in a self-operating network, a source of direct current having one pole connected to said armature and the other pole connected to a speed control rheostat, said speed control rheostat being in turn connected to the wiper of a balance rheostat having its resistance element substantially bridged across said winde ing for adjusting the relative speed of movement of said front contacts and a load cirouit including a back and a front contact of said relay.

References Cited in the file of this patent UNITED STATES PATENTS Holst Dec. 3, 1940 6 Garstang June 16, 1942 Ellis July 20, 1948 Wise Oct. 19, 1948 Hart July 24, 1951 Sandberg Mar. 13, 1956 George June 25, 1957 

